BSEG extract

BSEG is a cluster table and I need to improve the performance of the extract as given below. This is really taking a long time to run. Any suggestions as to how I can improve the performance?

SELECT BELNR

BUZEI

BSCHL

SHKZG

PRCTR

KOSTL

HKONT

DMBTR

WRBTR

SGTXT

FROM BSEG

INTO TABLE IBSEG

FOR ALL entries in IBKPF

WHERE BELNR = IBKPF-BELNR

AND HKONT in gl_acct.